The 20-year-old missed the bulk of pre-season after suffering an ankle injury in United’s first friendly at Darlington in mid-July when goalkeeper Fraser Forster knocked him.
It was a bitter blow for the Northern Ireland international, and he saw Alan Pardew pay £6m for Davide Santon (pictured right).
But he looks back saying "what happened is in the past now".
He is just glad to be back involved again after a frustrating couple of months on the sidelines.
Shane Ferguson: “It was disappointing, as I thought this season could be a great chance for me.
“But Ryan Taylor’s done fantastically and I’ll just have to keep impressing and give the manager a headache.
"I played 120 minutes against Forest and the fixture reminded me of last season’s third-round tie at Chelsea, when we won 4-3.
“The atmosphere was brilliant and I was just glad Colo put the ball in the back of the net.
“It was such a relief. Credit to the lads, they dug deep and the run is continuing.
“Before extra time, we just said to keep passing the ball and don’t make any mistakes. The lads did brilliantly and dug deep.
“It’s been an unbelievable start. The lads have put the work in and it’s showing in the games. Everyone’s done brilliantly.”